INTERGRATION CONSTRUCTION BETWEEN A BOILER AND A STEAM TURBINE AND METHOD IN PREHEATING OF THE SUPPLY WATER FOR A STEAM TURBINE AND IN ITS CONTROL

Description

[0001] The present invention relates to an integrated construction of a steam boiler and a steam turbine and a method in preheating the supply water for a steam turbine and in its controls according to the preambles of claims 1 and 3 respectively. Such a construction and method are known from document US-A-3 913 330.

[0002] The last heat face of a steam boiler before the smoke stack is either a flue-gas/air heat exchanger or an economizer. In the present application, a flue-gas/air heat exchanger is understood as a heat exchanger between flue gas and combustion air, in which the heat is transferred from the flue gas into the combustion air to preheat the combustion air. In the present application, an economizer is understood as a heat exchanger in which thermal energy is transferred from the flue gases into the supply water.

[0003] When a flue-gas/air heat exchanger is used, the supply water for the boiler can be preheated by means of bled steam from a steam turbine, whereby the efficiency of the steam turbine process is enhanced. A flue-gas/air heat exchanger, i.e. a heat exchanger, in which thermal energy is transferred from the flue gases directly into the combustion air is not usually used in small steam power plants because of its high cost.

[0004] When a flue-gas/air heat exchanger is not used, the flue gases of the steam boiler are cooled with the aid of an economizer before passing into the smoke stack. In such case, the supply water cannot be preheated with the aid of bled steam of the steam boiler because the preheating would raise the ultimate temperature of the flue gases and thereby, impair the efficiency of the boiler.

[0005] In an economizer of a steam boiler, heat is transferred from the flue gases into the supply water. A steam boiler provided with a combustion chamber is used as the steam boiler. A change in the temperature of the supply water in the economizer is lower than a change in the temperature on the flue-gas side. A temperature rise in the supply water is usually 40 to 50 per cent of the respective the temperature drop on the flue-gas side. Hence, a difference of temperature on the hot end of the economizer is considerably higher than on the cold end. A result of this observation is that, in addition to the heat obtained from the flue gases, different kind of heat can be transferred into the supply water. In a steam turbine process, it is advantageous to utilize bled steam for preheating the supply water.

[0006] The economizer of the steam boiler in a steam power plant is divided into two or more parts, the supply water being preheated in the preheaters of the high-pressure side provided between said economizer parts by the bled steam from the steam turbine.

[0007] With the aid of a connection, the integration of the steam boiler and the steam turbine process is made more efficient. By means of such arrangement, the flue gases of the steam boiler can be cooled efficiently, and simultaneously enhancing the efficiency of the steam turbine process.

[0008] The investment cost is lower than in an alternative provided with a flue-gas/air heat exchanger:

• improved controllability and boiler efficiency
• smaller boiler building
• lower cost of the boiler.

[0009] When a flue-gas/air heat-exchanger solution is unprofitable, an improved process can be implemented with the structure since the use of bled steam can be increased.

[0010] The arrangement is preferred especially in an instance in which the combustion air of the steam boiler is heated in one or more steam/air heat exchanger(s) connected in series and utilizing bled steam.

[0011] In a prior FI patent No. 101 163 of the applicant, the advantageous integration construction between the steam boiler and the steam turbine is known. It has proved to be useful that the temperature of the supply water flown through the economizers positioned in the flue-gas duct can be controlled. An amendment to the integration construction disclosed in the FI patent No. 101 163 is presented in the present application.

[0012] It is disclosed in the present application that by limiting the amount of bled steam of the preheater in the divided economizer, the integration degree of the steam turbine process can be controlled. The preheating is limited by the boiling temperature of the hottest economizer, and the lower limit is the closing of the bled. The method of control exerts an efficient impact on the electricity production but it slightly deteriorates the efficiency of the boiler when the bled steam use exceeds the scheduled value. A change in the degree of integration is of the order 10%. A change in the efficiency of the boiler is 2 to 3% at most.

[0013] By controlling the temperature of the supply water flowing through the economizer it is possible

(a) to control the ultimate temperature of the flue gas of the boiler as the power of the boiler changes and as the quality of the fuel varies

(b) to control the ultimate temperature of the supply water so that the ultimate temperature of the supply water after the economizer is as desired (being e.g. 10 to 20 °C below the boiling temperature).

[0014] Particularly when a soda recovery boiler is in question, the flue gases are highly soiling and corroding, and therefore, the soda recovery boilers cannot be provided with a flue-gas/air heat exchanger. The flue gases of the boiler are cooled by supplying supply water at about 120°C into the boiler. The preheating of the combustion air is important because of the combustion of black lye and therefore, the combustion air is heated with the aid of plant steam, typically to about 150 °C.

[0015] The above integration is not optimal considering the steam turbine process and therefore, the electricity power obtained from a back-pressure turbine remains low. As regards the boiler, an optimal situation prevails when the temperature of the flue gases exiting the boiler is as low as possible and no excessive soiling and corrosion of the heat faces is taking place yet. When the supply water supplied into the boiler is in a constant temperature, the temperature of the flue gases varies in accordance with the power level, quality of fuel and the soiling situation of the heat faces. An optimal temperature is reached only momentarily by partial power ratios.

[0016] As described above, the optimal manner of running the boiler is reached by integrating the soda recovery boiler and steam turbine process as follows. The combustion air is preheated, instead of the plant steam, with bled steams of the steam turbine to about 200°C, and between the economizers in the flue-gas duct of the boiler, a supply water preheater utilizing bled steam is positioned. By controlling the temperature of the supply water entering into the boiler with the aid of the amount of bled steam entering into the preheater, the ultimate flue-gas temperature of the boiler can be controlled as desired in all running situations.

[0017] The integration construction between a steam boiler and a steam turbine of the invention and the method in preheating the supply water of the steam turbine and in its control is characterized in what is presented in the claims.

[0018] The invention is described below referring to the advantageous embodiments of the invention illustrated in the drawings of the accompanying figures.

[0019] Figure 1 presents as a schematic diagram an integration construction between a boiler and a steam turbine.

[0020] Figure 2 presents a decrease of the flue-gas temperature in a flue-gas duct and an increase of temperature in the supply water of the economizer in a control of the invention.

[0021] Figure 1 presents an integration construction of the invention between a steam boiler and a steam turbine, comprising a steam boiler, such as soda recovery boiler, to which fuel is brought as shown by arrow M₁. The boiler is indicated by reference numeral 10. The evaporator is indicated by reference numeral 190 and the superheater thereafter in a connector 12a₁ by reference numeral 120. The flue gases are discharged during a second draught 10a from the boiler 10 through a smoke stack 100 into the outside air as shown by arrow L₁. The second draught 10a is the part of the boiler which comprises heat faces prior to the smoke stack 100. Superheated steam is conducted to the steam turbine 11 along the connector 12a₁ and the steam turbine 11 is arranged to rotate a generator G producing electricity. From the steam turbine 11, connectors 13a₁ and 13a₂ are provided for bled steams and a connector 13a₃ into a condensator for exit steams or back-pressure steam travelling into an industrial process. The connector 13a₁ is branched into branch connectors 13a_1.1 and 13a_1.2, of which the connector 13a_1.1 conducts to a preheater 14 of the supply water running in the connector 19 and the connector 13a_1.2 conducts to a preheater 15a₁ of the combustion air which is provided with a return connector 13b₂ to the supply water tank 17. From the supply water preheater 14, a return connector 13b₂ is provided into the supply water tank 17. The combustion air is conducted along a connector or an air duct 16 via combustion air preheaters 15a₁ and 15a₂ positioned in series in the combustion chamber K of the boiler 10.

[0022] In the integration construction, the temperature of the supply water is continuously raised when it is flowing in a first economizer section 20a₁ and from the first economizer section 20a₁ to the supply water preheater 14 and therethrough to a second economizer section 20a₂. In the preheater 14, the supply water is heated with the aid of thermal energy obtained from bled steams.

[0023] From the steam turbine 11, a connector 13a₂ is furthermore provided for bled steam, which is branched into branch connectors 13a_2.1, 13a_2.2. The connector 13a_2.1 leads to a second combustion air preheater 15a₂. From the air preheater 15a₂, a discharge connector 13b₃ is provided to the supply water tank 17. The connector 13a_2.2 leads to the supply water tank 17. The discharge steam connector 13a₃ of the steam turbine 11 is lead to a condensator 18. On the outlet side of the condensator 18, the connector 13a₃ is provided with a pump Pi to pump water into the supply water tank 17 from the condensator 18.

[0024] A pump P₂ is connected to a connector 19 leading from the supply water tank 17 to a first economizer section 20a₁ of the economizer 20 in the flue-gas duct 10a, said first economizer section being further connected to a second economizer section 20a₂, which economizer sections 20a₁ and 20a₂ are in this manner in series in relation to each other and between which economizer sections 20a₁ and 20a₂, a preheater 14 is located to transfer the energy from the bled steam into the supply water. Thus, the economizer 20 is made at least of two sections, and the first economizer section 20a₁, the supply water preheater 14 and the second economizer section 20a₂ are connected in series in relation to each other. Thermal energy is transferred in the preheater 14 either directly from the steams into the supply water or indirectly via a medium, for instance water, into the supply water. Therefore, the preheater 14 is a heat exchanger in which thermal energy is transferred into the supply water.

[0025] By controlling the amount of bled steam to the preheater 14 with a valve 21, the temperature of the supply water entering into the second economizer section 20a₂ can be regulated efficiently in different running conditions of the boiler 10.

[0026] As in Figure 2, the water temperature of the supply water entering into the hot economizer section 20a₂ changes due to the control. This affects the cooling power of the flue gases as a result of changed temperature differences in the heat transfer and therethrough, the influence of the control is transmitted to the ultimate temperature of the flue gases. On the inlet side of the economizer section 20a₁ and on the outlet side of the flue-gas duct 10a, the flue-gas temperature is marked by T₁' and the temperature of the supply water by T₁". On the outlet side of the second economizer section and on the inlet side of the flue-gas duct the markings of Figure 2 are as follows: the flue-gas temperature is T₂' and the supply water temperature is T₂". The flue-gas duct 10a may comprise temperature sensors: a temperature sensor E₂ measuring the temperature on the inlet side of the flue-gas duct (when viewed in the flow direction L₁ of the flue gas), and a temperature sensor E₁ measuring the temperature of the flue gas on the outlet side of the flue-gas duct 10a. In addition, the apparatus may comprise temperature sensors in the connector of the supply water. The temperature can be measured from the supply water after the first economizer section 20a₁ before the second economizer section 20a₂ and from the supply water after the second economizer section 20a₂ when viewed in the flow direction L₂ of the supply water. The flow direction of the supply water in the connector 19 is marked by arrow L₂ in the figure 1.

[0027] In the method in preheating the supply water of a steam turbine and in its control, the procedure is as follows. The supply water is conducted into an economizer 20 of the steam boiler 10 provided with a combustion chamber K, where heat is transferred in a heat exchanger from the flue gases into the supply water. The economizer 20 is arranged to be positioned, at least in part, on its heat faces in a flue-gas duct 10a of the steam boiler 10. At least a two-section economizer 20a₁, 20a2 is used for heating the supply water. The first preheating of supply water is carried out with the aid of thermal energy taken from the flue gases of the boiler in the first economizer section 20a₁. The second preheating step 14 takes place between the economizer sections 20a₁, 20a₂, where the preheating of supply water is carried out from bled steams with the aid of thermal energy provided either directly or indirectly. The supply water preheated with the aid of bled steams is conducted into the second economizer section 20a₂ and further to a vaporizer 190 and a superheater 120 and further, in the form of steam, to the steam turbine 11 to rotate the electric generator G and to produce electricity. In the method, the temperature of the supply water is raised continuously when it is running in the first economizer section 20a₁ and from the first economizer section 20a₂ to the preheating section 14, and from said preheating section 14 to the economizer section 20a₂, in which the supply water is hotter. In the method, also the combustion air is preheated with the aid of the energy acquired from bled steams. In the method, the bled-steam flow made to flow to the preheater 14 of the supply water is controlled for controlling the temperature of the supply water in the connector 19. The flow quantity of the bled steam in the connector 13a_1.1 is controlled with a valve 21. The bled-steam flow to the preheater 14 is controlled on the basis of temperature measurements, that is, by measuring the temperature T₁', T₂' of the flue gases made to flow in the flue-gas duct 10a and/or the temperature T₁", T₂" of the supply water in the connector 19.

Claims

1. An integrated construction of a steam boiler and a steam turbine provided with a combustion chamber, in which

- steam is conducted from a steam boiler (10) along a connector to a steam turbine (11) for rotating an electric generator (G) generating electricity,

- the supply water circulated through the steam boiler (10) is vaporized in a vaporizer (190) located in the steam boiler (10) and superheated in a superheater (120),

- the supply water is conducted into the boiler through an economizer (20) acting as a heat exchanger, in which heat is transferred from the flue gases of the boiler into the supply water,

- the economizer (20) is provided with at least two sections, comprising at least one first economizer section (20a₁) and at least one second economizer section (20a₂),

- the supply water is conducted from the first economizer section (20a₁) to a supply water preheater (14) formed from the heat exchanger, where thermal energy is transferred from the bled steams of the steam turbine either directly or via a medium, advantageously water, into the supply water,

- the supply water preheated with the bled steams of the steam turbine is conducted in the steam boiler (10) to the second economizer section (20a₂) and further, in the form of steam, to the vaporizer and the superheater, and therethrough, to the steam turbine,

in which integrated construction the temperature of the supply water is raised continuously as the supply water is flowing in the first economizer section (20a₁) and from the first economizer section (20a₁) to the supply water preheater (14) and therethrough to the second economizer section (20a₂), characterized in that the connector (13a_1.1) leading from the turbine to the supply water preheater (14) comprises a valve (21) for controlling the bled-steam flow to the preheater (14).

2. An integrated construction according claim 1, characterized in that the flow quantity of bled steam to the preheater (14) is controlled with valves (21).

3. A method in the preheating of the supply water for a steam turbine and in its control, in which

- the supply water is conducted into an economizer (20) of a steam boiler (10) provided with a combustion chamber (K), in which heat is transferred in a heat exchanger from flue gases into the supply water,

- the economizer (20) is arranged to be located, by its heat faces, at least partly in the flue-gas duct (10a) of the steam boiler (10),

- an economizer (20a₁, 20a₂) provided with at least two sections is used for heating the supply water,

- preheating of the first supply water is carried out with the aid of thermal energy acquired from the flue gases of the boiler in the first economizer section (20a₁),

- the second preheating phase (14) takes place between the economizer sections (20a₁, 20a₂), where the preheating of the supply water is carried out with the aid of thermal energy acquired from the bled steams of the steam turbine either directly or indirectly,

- the supply water preheated with the aid of bled steams is conducted to the second economizer section (20a₂) and further, to a vaporizer (190) and a superheater (120) and, further in the form of steam, to the steam turbine (11) for rotating the electric generator (G) and for producing electricity,

- the temperature of the supply water is raised continuously as it is flowing in the first economizer section (20a₁) and from the first economizer section (20a₂) to the preheating section (14), and from said preheating section (14) to the second economizer section (20a₂) with hotter supply water,

- also the combustion air is preheated with the aid of energy acquired from bled steams,

characterized in that the temperature of the supply water entering the second economiser section (20a₂) is controlled by controlling the bled-steam flow made to flow to the supply water preheater (14).

4. A method according to the preceding claim, characterized in that the flow quantity of bled steam in the connector (13a_1.1) from the turbine to the preheater (14) is controlled with a valve (21).

5. A method according to claim 3 or 4, characterized in that the bled-steam flow to the preheater (14) is controlled on the basis of temperature measurements, that is, by measuring the temperature (T₁', T₂') of the flue gases made to flow in the flue-gas duct (10a) and/or the supply water temperature (T₁", T₂") in the connector (19) from the supply water tank (17) to the vaporiser.

Revendications

1. Construction intégrée d'une chaudière à vapeur et d'une turbine à vapeur dotée d'une chambre de combustion, dans laquelle

- la vapeur est amenée d'une chaudière à vapeur (10) le long d'un connecteur à une turbine à vapeur (11) destinée à mettre en rotation un générateur électrique (G) générant de l'électricité,

- l'eau d'alimentation circulant à travers la chaudière à vapeur (10) est vaporisée dans un vaporisateur (190) placé dans la chaudière à vapeur (10) et surchauffée dans un surchauffeur (120),

- l'eau d'alimentation est amenée à l'intérieur de la chaudière à travers un économiseur (20) agissant comme un échangeur de chaleur, dans lequel la chaleur est transférée des gaz d'évacuation de la chaudière à l'intérieur de l'eau d'alimentation,

- l'économiseur (20) est pourvu d'au moins deux sections, comprenant au moins une première section d'économiseur (20a₁) et au moins une seconde section d'économiseur (20a₂),

- l'eau d'alimentation est amenée de la première section d'économiseur (20a₁) à un préchauffeur d'eau d'alimentation (14) formé à partir de l'échangeur de chaleur, dans lequel l'énergie thermique est transférée des vapeurs de soutirage de la turbine à vapeur soit directement soit via un milieu, de manière avantageuse de l'eau, à l'intérieur de l'eau d'alimentation,

- l'eau d'alimentation préchauffée avec les vapeurs de soutirage de la turbine à vapeur est amenée dans la chaudière à vapeur (10) à la seconde section d'économiseur (20a₂) et en outre, sous forme de vapeur, au vaporisateur et au surchauffeur, et à travers ceux-ci, à la turbine à vapeur,

construction intégrée dans laquelle la température de l'eau d'alimentation est élevée en continu à mesure que l'eau d'alimentation s'écoule dans la première section d'économiseur (20a₁) et depuis la première section d'économiseur (20a₁) au préchauffeur d'eau d'alimentation (14) et à travers ceux-ci à la seconde section d'économiseur (20a₂), caractérisée en ce que
le connecteur (13a_1.1) menant de la turbine au préchauffeur d'eau d'alimentation (14) comprend une soupape (21) destinée à contrôler l'écoulement de vapeur de soutirage en direction du préchauffeur (14).

2. Construction intégrée selon la revendication 1, caractérisée en ce que la quantité d'écoulement de vapeur de soutirage en direction du préchauffeur (14) est contrôlée avec les soupapes (21).

3. Procédé de préchauffage de l'eau d'alimentation pour une turbine à vapeur et de son contrôle, dans lequel

- l'eau d'alimentation est amenée à l'intérieur d'un économiseur (20) d'une chaudière à vapeur (10) dotée d'une chambre de combustion (K), dans laquelle la chaleur est transférée dans un échangeur de chaleur des gaz d'évacuation à l'intérieur de l'eau d'alimentation,

- l'économiseur (20) est agencé pour être placé, par ses faces de chauffage, au moins en partie dans le conduit de gaz d'évacuation (10a) de la chaudière à vapeur (10),

- un économiseur (20a₁, 20a₂) pourvu d'au moins deux sections est utilisé pour chauffer l'eau d'alimentation,

- le préchauffage de la première eau d'alimentation est réalisé à l'aide d'une énergie thermique obtenue des gaz d'évacuation de la chaudière dans la première section d'économiseur (20a₁),

- la seconde phase de préchauffage (14) a lieu entre les sections d'économiseur (20a₁, 20a₂), dans lesquelles le préchauffage de l'eau d'alimentation est réalisé à l'aide d'une énergie thermique obtenue des vapeurs de soutirage de la turbine à vapeur soit directement soit indirectement,

- l'eau d'alimentation préchauffée à l'aide des vapeurs de soutirage est amenée à la seconde section d'économiseur (20a₂) et en outre, à un vaporisateur (190) et à un surchauffeur (120) et, en outre, sous forme de vapeur, à la turbine à vapeur (11) destinée à mettre en rotation le générateur électrique (G) et à produire de l'électricité,

- la température de l'eau d'alimentation est élevée en continu à mesure qu'elle s'écoule dans la première section d'économiseur (20a₁) et de la première section d'économiseur (20a₂) à la section de préchauffage (14), et de ladite section de préchauffage (14) à la seconde section d'économiseur (20a₂) avec de l'eau d'alimentation plus chaude,

- l'air de combustion est également préchauffé à l'aide d'une énergie obtenue des vapeurs de soutirage,

caractérisé en ce que la température de l'eau d'alimentation pénétrant dans la seconde section d'économiseur (20a₂) est contrôlée en contrôlant l'écoulement de vapeur de soutirage réalisé pour s'écouler en direction du préchauffeur d'eau d'alimentation (14).

4. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que la quantité d'écoulement de vapeur de soutirage dans le connecteur (13a_1.1) provenant de la turbine en direction du préchauffeur (14) est contrôlée avec une soupape (21).

5. Procédé selon la revendication 3 ou 4, caractérisé en ce que l'écoulement de vapeur de soutirage en direction du préchauffeur (14) est contrôlé sur la base des mesures de température, c'est-à-dire, en mesurant la température (T₁', T₂') des gaz d'évacuation amenés à s'écouler dans le conduit de gaz d'évacuation (10a) et/ou la température d'eau d'alimentation (T₁", T₂") dans le connecteur (19) du réservoir d'eau d'alimentation (17) au vaporisateur.

Ansprüche

1. Integrierte Konstruktion eines Dampfkessels und einer mit einer Verbrennungskammer vorgesehenen Dampfturbine, in der
Dampf von einem Dampfkessel (10) entlang einem Verbindungsstück zu einer Dampfturbine (11) zum Drehen eines Generators (G), der Strom erzeugt, geleitet wird,
das Speisewasser, das durch den Dampfkessel (10) zirkuliert, in einem Verdampfer (190) verdampft wird, der in dem Dampfkessel (10) angeordnet ist, und in einem Überhitzer (120) überhitzt wird,
das Speisewasser in dem Dampfkessel durch einen Ekonomiser (20) geleitet wird, der als ein Wärmetauscher wirkt, in dem die Wärme von den Rauchgasen des Dampfkessels zu dem Speisewasser übertragen wird,
der Ekonomiser (20) mit zumindest zwei Bereichen vorgesehen ist, die zumindest einen ersten Ekonomiserbereich (20a₁) und einen zweiten Ekonomiserbereich (20a₂) aufweisen,
das Speisewasser von dem ersten Ekonomiserbereich (20a₁) zu einem Speisewasservorwärmer (14) geleitet wird, der aus dem Wärmetauscher ausgebildet ist, in dem thermische Energie von den abgezapften Dämpfen der Dampfturbine entweder direkt oder über ein Medium, vorteilhafterweise Wasser, zu dem Speisewasser übertragen wird,
das Speisewasser, das mit den abgezapften Dämpfen der Dampfturbine vorgewärmt wird, in den Dampfkessel (10) zu dem zweiten Ekonomiserbereich (20a₂) und weiter in der Form von Dampf zu dem Verdampfer und dem Überhitzer und durch diese hindurch zu der Dampfturbine geleitet wird,
wobei in der integrierten Konstruktion die Temperatur des Speisewassers kontinuierlich steigt, wenn das Speisewasser in den ersten Ekonomiserbereich (20a₁) und von dem ersten Ekonomiserbereich (20a₁) zu dem Speisewasservorwärmer (14) und durch diese hindurch zu dem zweiten Ekonomiserbereich (20a₂) strömt,
dadurch gekennzeichnet, dass
das Verbindungsstück (13a_1.1), das von der Turbine zu dem Speisewasservorwärmer (14) führt, ein Ventil (21) zum Steuern des abgezapften Dampfstroms zu dem Vorwärmer (14) aufweist.

2. Integrierte Konstruktion gemäß Anspruch 1,
dadurch gekennzeichnet, dass
die Strommenge von abgezapftem Dampf zu dem Vorwärmer (14) mit den Ventilen (21) gesteuert wird.

3. Verfahren zum Vorwärmen des Speisewassers für eine Dampfturbine und zu ihrer Steuerung, in dem
das Speisewasser in einen Ekonomiser (20) eines mit einer Verbrennungskammer (K) vorgesehenen Dampfkessels (10) geleitet wird, in dem Wärme in einem Wärmetauscher von Rauchgasen zu dem Speisewasser übertragen wird,
der Ekonomiser (20) angeordnet ist, um durch seine Heizflächen zumindest zum Teil in dem Rauchgaskanal (10a) des Dampfkessels (10) zu liegen,
ein Ekonomiser (20a₁, 20a₂), der mit mindestens zwei Abschnitten vorgesehen ist, zum Erwärmen des Speisewassers verwendet wird,
ein Vorwärmen des ersten Speisewassers mit der Hilfe von thermischer Energie durchgeführt wird, die von den Rauchgasen des Kessels in dem ersten Ekonomiserbereich (20a₁) gewonnen wird,
die zweite Vorwärmstufe (14) zwischen den Ekonomiserbereichen (20a₁, 20a₂) stattfindet, in denen das Vorwärmen des Speisewassers mit der Hilfe von thermischer Energie durchgeführt wird, die von den abgezapften Dämpfen der Dampfturbine entweder direkt oder indirekt gewonnen wird,
das Speisewasser, das mit der Hilfe von abgezapften Dämpfen vorgewärmt wird, zu dem zweiten Ekonomiserbereich (20a₂) und weiter zu einem Verdampfer (190) und einem Überhitzer (120) und weiter in der Form von Dampf zu der Dampfturbine (11) zum Drehen des Generators (G) und zum Erzeugen von Strom geleitet wird,
die Temperatur des Speisewassers kontinuierlich steigt, wenn es in den ersten Ekonomiserbereich (20a₁) und von dem ersten Ekonomiserbereich (20a₂) zu dem Vorwärmbereich (14) und von dem Vorwärmbereich (14) zu dem zweiten Ekonomiserbereich (20a₂) als heißeres
Speisewasser strömt,
auch die Verbrennungsluft mit der Hilfe von Energie vorgewärmt wird, die von den abgezapften Dämpfen gewonnen wird,
dadurch gekennzeichnet, dass
die Temperatur des Speisewassers, das in den zweiten Ekonomiserbereich (20a₂) eintritt, durch Steuern des abgezapften Dampfstroms gesteuert wird, der geschaffen ist, zu dem Speisewasservorwärmer (14) zu strömen.

4. Verfahren gemäß dem vorhergehenden Anspruch,
dadurch gekennzeichnet, dass
die Strommenge von abgezapftem Dampf in dem Verbindungsstück (13a_1.1) von der Turbine zu dem Vorwärmer (14) mit einem Ventil (21) gesteuert wird.

5. Verfahren gemäß Anspruch 3 oder 4,
dadurch gekennzeichnet, dass
der angezapfte Dampfstrom zu dem Vorwärmer (14) auf der Grundlage von Temperaturmessungen gesteuert wird, das heißt durch Messen der Temperatur (T₁', T₂') der Rauchgase, die geschaffen sind, in dem Rauchgasrohr (10a) zu strömen, und/oder der Temperatur (T₁", T₂") des Speisewassers, das geschaffen ist, in dem Verbindungsstück (19) von dem Behälter (17) des Speisewassers zu dem Verdampfer zu strömen.

Drawing